Access is multiuser databse, all you need to do is to insure that you don't work at the same time in the same record. You can accomplish that by adding a field, for example integer, and every time you open the record to edit it you will check first if that field is 1 or 0. If is 0 you set it to 1 and then you edit it. Then if the second user tries to open it for editing he will see that the record is 1, that means the record is under editing. Don't forget to refresh data before ask to edit if it's a grid you working. I hope you got the point.

Hi and thank you, i thought i gona split the tables so they would be on the backend - the forms and queries i would leave on the frontend this way it should be posible to use the database over the network,

so i need to split the database but how?

for example invoice numbers allready used i could conrol the way smart media recommends

or may its better to use SQL Server or Oracle they do all of the number crunching in the background?

If you like to work over Internet it's better to use an SQL database, i personally always use MySQL. If you want to work over local network an Access with mapped pubdir will do the work.

so i need to split the database but how?

Why, i don't think there is a reason to split the database, don't forget that is more hard to maintain 2 than 1 database.
All you have to do is to change the way you GUI works in order not to have conflicts with the DBPro grid with more than 1 users.